The present invention concerns a spinneret for spinning cellulose solutions.
It is known from U.S. Pat. No. 2,179,181 that tertiary amine-oxides are capable of dissolving cellulose and that cellulose fibres can be obtained from these solutions by precipitation. A process for the preparation of such solutions is known for example from EP-A 0 356 419. According to this publication, a suspension of cellulose is firstly prepared in aqueous tertiary amine-oxide. The amine-oxide contains up to 40 weight % water. The aqueous cellulose suspension is heated and water is removed under reduced pressure until the dissolves. The process is carried out in a specially-developed stirring device which can be evacuated.
When preparing cellulose fibres, it is known from DE-A 2 844 163 that an air gap can be located between the spinning die, ie, the spinneret, and the precipitation bath to achieve drawing at the die. This drawing at the die is necessary because drawing of the fibres becomes very difficult after contact of the shaped spinning solution with the aqueous precipitation bath. The fibre structure which is set in the air gap is fixed in the precipitation bath.
A process of the type mentioned at the start is known from DE-A 2 830 685, wherein a solution of cellulose in a tertiary amine-oxide is shaped in hot condition to give filaments which are cooled with air and then introduced into a precipitation bath in order to precipitate the dissolved cellulose. The surface of the spun fibres is also wetted with water to reduce their tendency to adhere to neighbouring fibres.
It has been shown that all processes in the prior art concerning the formation of filaments and the textile properties of the fibres are unsatisfactory. On account of the small spinning gap between the spinneret and the precipitation bath, which is in the region of a few centimeters, and the short period of time available in which the properties of the fibre can be adjusted, it is difficult to achieve for instance a uniform titre and a uniform strength and elongation for all the filaments in the fibre bundle and for the fibres obtained after precipitation. This particularly occurs when spinning is carried out at high capacity, ie, at high fibre density.